SMTP connection fails with response -1 in Aria Operations

Products

• VCF Operations

Issue/Introduction

When configuring the Standard Email Plugin in Aria Operations, the connection test fails with the following symptoms:

• Error message: Email test error: [Could not connect to SMTP host: ####, port: 25, response: -1]
• Running curl -v telnet://####:25 from the Aria Operations appliance shows the connection is established but immediately dropped: * shutting down connection #0.
• The same telnet test from other components (like vCenter) succeeds and returns the SMTP banner.

Environment

VMware Aria Operations 8.x

Cause

The SMTP server or an intermediate firewall is actively terminating the connection. This typically occurs because the Aria Operations appliance IP address is not included in the SMTP server's trusted relay list or a firewall policy is dropping traffic from that specific IP.

Resolution

To resolve this issue, ensure the Aria Operations appliance IPs are whitelisted on the SMTP relay server and any intermediate firewalls.

1. Identify the IP addresses of all nodes in the Aria Operations cluster.
2. Contact the internal Networking or SMTP/Exchange administration team.
3. Request that the SMTP relay (e.g., port 25 or 587) allow traffic originating from the Aria Operations IP addresses.
4. Verify the fix by running the telnet command from the Aria Operations CLI: curl -v telnet://[SMTP_SERVER_IP]:25
5. Once the connection remains stable and returns the SMTP banner, re-test the outbound configuration in the Aria Operations UI.

For more details on configuring outbound settings, see Adding outbound Notification Plug-Ins in VMware Aria Operations.